This invention relates to troposcatter communications systems and in particular to a method and means for aligning the antennas of such systems.
The conventional approach to aligning troposcatter system antennas in the past has been to maximize the received signal power. However, because of deep, persistent fading on scatter channels, the proper rotating angle alignment for each antenna is difficult to determine by this method and both antennas are often fixed in less than the optimum pointing position.
Accordingly, there currently exists the need for troposcatter antenna alignment techniques that do not depend on received signal power. It is also desirable that such techniques be practiced without the use of complex computer programs or expensive special purpose computers.
Improved troposcatter alignment techniques achieved by alignment methods utilizing doppler shift characteristics instead of signal power maximization and crosscorrelation techniques and data processing procedures instead of computer processing have been developed and are described in detail in the patent application entitled Precision Antenna Alignment Procedure of William P. Birkemeier et al Ser. No. 865,269, filed Dec. 28, 1977, now U.S. Pat. No. 4,170,011. Although this technique overcomes some of the deficiencies of prior art approaches and represents a significant step forward in the art, it still requires sophisticated processing equipment as well as the defocusing and focusing of the transmitted and received beams.
The present invention comprehends a new technique to align troposcatter antennas, specifically of the phased-array type. The technique does not require the troposcatter system to be coherent and able to transmit a monochoromatic signal, nor does it require beam defocusing as in the above referenced patent application.